As part of a standardized research sequence in the NIHM intramural clinical program located at Saint Elizabeths, patients with schizophrenia are withdrawn from neuroleptic medication and then (after clinical relapse) treated with a fixed dose of haloperidol. This has in turn allowed initiation of a variety of studies regarding the pharmacokinetics of haloperidol. Other pharmacological issues examined in these patients are drug-drug interactions (specifically involving haloperidol and a number of other drugs, including nicotine, caffeine, retinoic acids, and dopaminergic agonists). In addition, basic science investigations regarding these drugs are being conducted.